[NTG-context] strange unknown reference problem

Hi all, I got a strange "unknown reference" problem with the following simple example: %%%%%%%%%%%%%%%%% \starttext \placeformula[eq:haha] \startformula a^2 + d^2 = c^2 \stopformula haha \in[eq:haha] \stoptext %%%%%%%%%%%%%%%%% After 3 iterations, I saw this message in the log file: references : unknown reference [][eq:haha] I am using luatex beta-0.43.0-2009081911 Got the same problem with context version from 2009.6.14 to the latest beta. I also tried deleting everything and re-install the minimal dist., but still can't solve the problem. I wonder if anyone else has this problem, or it only occurs to me. Thanks a lot. regards, shenchen